Contents 1. Introduction
AN inverter topology for high voltage high power applications that seems to be gaining interest lately is the multilevel inverter. The main feature of a multilevel inverter is its ability to reduce the voltage stress on each power device due to the utilization of multiple levels on the DC bus. This is especially important when a high DC bus voltage is imposed by an application. There are several types of multilevel inverters but the one considered in this paper is the modular structured multilevel inverter (MSMI). The structure of the MSMI is not only simple and modular but also requires the least number of components compared to other types of multilevel inverters. This in tum, provides the flexibility in extending the MSMI to higher Dumber of levels without undue increase in circuit complexity as well as facilitates packaging [1]. It must be realized however that an important requirement of the MSMI in applications involving real power transfer is DC sources that are isolated from one another. Thus, the MSMI topology is very much suitable for high power AC power supply applications particularly in power conditioning systems for alternate/renewable sources of energy such as PV arrays and fuel cells due to the originally isolated DC voltages that are available from these sources. To make an impact in future energy supply, it is inevitable for these energy sources to produce high DC voltages. The potential of the MSMI in high power UPS systems is also promising as future designs see the prospect of acquiring DC sources from fuel cells instead of batteries due to the indefinitely operation feature of the latter.
